A Bypass of the Firefox POST Redirection Bug

I’m happy to report that we have found a way of bypassing the Firefox POST redirection bug discussed in the previous post, obviating the need for code changes to cope with the redirection replay by Firefox when the user clicks the back button. While waiting for the bug to be fixed, this will simplify the implementation of web apps that rely on POST redirection, including apps that use cryptographic authencation or federated login. We have revised again the sample web app demoed at the last IIW, this time to simplify it by taking advantage of the bug bypass.

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Cryptographic Authentication Is Not That Easy After All

Updated May 13 as shown below.

At the last Internet Identity Workshop (IIW) we gave a demo of a sample web app that featured cryptographic authentication, and argued that implementing cryptographic authentication is easy. Later, in the blog post Easy, Password-Free, Cryptographic Authentication for Web Applications I discussed the code of the sample web app and said that cryptographic authentication provides a “simple alternative” to authentication with a password. The issues discussed in the post, however, were not simple! Since then we have had to revise the code of the demo several times to fix bugs and, in the process, we have come to realize that cryptographic authentication is not that easy after all. It does not take much code, but it requires a lot of attention to detail to avoid a variety of pitfalls.

In this post I recapitulate the pitfalls that we have encountered (some of which were already discussed in the earlier post) and explain how we avoid them in the latest version of the demo code.

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Easy, Password-Free, Cryptographic Authentication for Web Applications

Update (May 11). The demo code mentioned below has been updated to fix bugs. If you find any additional bugs please report them through the contact form or by posting to the PJCL forum. The date of the latest update will be shown in the PJCL page. Please see also the blog post Cryptographic Authentication Is Not That Easy After All.

For years there has been consensus that passwords have to go. To the many reasons for not using password authentication, the European GDPR will add, when it goes into effect on May 25, stringent requirements to notify users and regulators when passwords are compromised, backed by substantial fines. And yet, passwords are still the dominant authentication technology for web applications. This is because the alternatives that have been proposed and tried so far are complicated and expensive to implement. But there is a simple alternative that you can implement yourself, if you are a web application developer: cryptographic authentication with a digital-signature key pair stored in the browser.

At last week’s Internet Identity Workshop (IIW) we showed how easy it is to implement this alternative. We gave a demo of a sample web application, exercising the user interface and looking at the code. The sample application was implemented in Node.js and used the Pomcor JavaScript cryptographic library (PJCL) on the client and server sides. The code of the sample application, which we will refer to as the demo code, can be found in the PJCL page of the Pomcor site (subsequently modified as explained below to accommodate Internet Explorer).

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PJCL Can Now Be Used in Node.js Server-Side Code Exactly as in the Browser

We have just released Revision 1 of Version 0.9.1 of the Pomcor JavaScript Cryptographic library (PJCL), which changes the way in which library functions are defined, making it easier to use PJCL in Node.js. In this post I describe the change and explain why it is important for full stack web application development.

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Second Release of PJCL Expands Functionality Following NIST Cryptographic Specifications

Today we have released version 0.9.1 of the Pomcor JavaScript Crytpographic Library (PJCL). The initial public release provided digital signature functionality, which we had been using internally for our own research on authentication and identity proofing. This release adds key agreement and key derivation functionality. The next release will provide symmetric and asymmetric encryption primitives, including AES and RSA. To be notified of future releases you may sign up for the user forum, subscribe to this blog, or follow me on Twitter (@fcorella).

PJCL can be used in any JavaScript environment, both client-side (e.g. in a browser) and server-side (e.g. under Node.js). It comes with extensive documentation on the functionality that it provides, which includes:

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Pomcor Releases JavaScript Cryptographic and Big Integer Library

We have just released a beta version of a JavaScript cryptographic library usable in any JavaScript environment and based on very fast big integer arithmetic functionality that may be of interest in its own right.

The Pomcor JavaScript Cryptographic Library (PJCL) is available free of charge for any kind of use, but not under a traditional open source license. The traditional open source paradigm encourages contributions by the developer community at large, but we believe that this paradigm is not well suited to cryptography. To protect the integrity of the cryptographic code, the license prohibits modification of the cryptographic functions.

We have been using the library internally for our own research on authentication and identity proofing, and this first release includes symmetric and asymmetric digital signature functionality, including HMAC, DSA, and ECDSA with NIST curves. Future releases will provide broader cryptographic functionality, including encryption and key exchange. We believe that the library provides the only available JavaScript implementation of DSA, which is important to those wary of the opportunities for hiding backdoors that might be provided by elliptic curve technology.

The underlying big integer functionality includes Karatsuba multiplication. Continue reading “Pomcor Releases JavaScript Cryptographic and Big Integer Library”

Storing Cryptographic Keys in Persistent Browser Storage

This blog post is a companion to a presentation made at the 2017 International Cryptographic Module Conference and refers to the presentation slides, revised after the conference. Karen Lewison is a co-author of the presentation and of this blog post.

Slide 2: Key storage in web clients

Most Web applications today use TLS, thus relying on cryptography to provide a secure channel between client and server, and to authenticate the server to the client by means of a cryptographic credential, consisting of a TLS server certificate and its associated private key. But other uses of cryptography by Web applications are still rare. Client authentication still relies primarily on traditional username-and-password, one-time passwords, proof of possession of a mobile phone, biometrics, or combinations of two or more of such authentication factors. Web payments still rely on a credit card number being considered a secret. Encrypted messaging is on the rise, but is not Web-based.

A major obstacle to broader use of cryptography by Web applications is the problem of where to store cryptographic keys on the client side. Continue reading “Storing Cryptographic Keys in Persistent Browser Storage”

What kind of “encrypted fingerprint template” is used by MasterCard?

In a press release, MasterCard announced yesterday an EMV payment card that features a fingerprint reader. The release said that two trials have been recently concluded in South Africa and, after additional trials, a full roll out is expected this year.

In the United States, EMV chip cards are used without a PIN. The fingerprint reader is no doubt intended to fill that security gap. But any use of biometrics raises privacy concerns. Perhaps to address such concerns, the press release stated that a fingerprint template stored in the card is “encrypted”.

That’s puzzling. If the template is encrypted, what key is used to decrypt it before use?

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Revocable Biometrics Discussion at the Internet Identity Workshop

One thing I like about the Internet Identity Workshop (IIW) is its unconference format, which allows for impromptu sessions. A discussion during one session can raise an issue that deserves its own session, and an impromptu session can be called the same day or the following day to discuss it. A good example of this happened at the last IIW (IIW XXII), which was held on April 26-28, 2016 at the Computer History Museum in Mountain View, California.

During the second day of the workshop, a participant in a session drew attention to one of the dangers of using biometrics for authentication, viz. the fact that biometrics are not revocable. This is true in the sense that you cannot change at will the biometric features of the human body, and it is a strong reason for using biometrics sparingly; but I pointed out that there is something called “revocable biometrics”. Continue reading “Revocable Biometrics Discussion at the Internet Identity Workshop”

NSA’s FAQs Demystify the Demise of Suite B, but Fail to Explain One Important Detail

Last July, the National Security Agency (NSA) issued CNSS Advisory Memorandum 02-15, available at the Advisory Memoranda page, updating the list of cryptographic algorithms that can be used in National Security Systems (NSS). A subsequent document referred to the new algorithms as the Commercial National Security Algorithm Suite (CNSA Suite), which replaces Suite B. The transition to the CNSA Suite took place two months before a Suite B deadline to discontinue the use of RSA, DH and DSA and rely exclusively on ECC algorithms for public key cryptosystems. The subsequent document explained the motivation for the transition by saying that “the growth of elliptic curve use has bumped up against the fact of continued progress in the research on quantum computing, which has made it clear that elliptic curve cryptography is not the long term solution many once hoped it would be,” and announced “preliminary plans” for a future transition to quantum-resistant algorithms.

This abrupt change of course, following many years of promoting ECC, took the cryptographic community by surprise. Continue reading “NSA’s FAQs Demystify the Demise of Suite B, but Fail to Explain One Important Detail”